U.S. patent application number 12/059786 was filed with the patent office on 2009-02-05 for cylindrical molded article, lens barrel, camera, and injection mold.
Invention is credited to Shouichi Irie, Makoto Iyoda, Suguru Nakao.
Application Number | 20090034096 12/059786 |
Document ID | / |
Family ID | 40337845 |
Filed Date | 2009-02-05 |
United States Patent
Application |
20090034096 |
Kind Code |
A1 |
Iyoda; Makoto ; et
al. |
February 5, 2009 |
CYLINDRICAL MOLDED ARTICLE, LENS BARREL, CAMERA, AND INJECTION
MOLD
Abstract
A drive frame 34 as a cylindrical molded article has a drive
frame main body 34a, three first cam grooves 34c, three second cam
grooves 34d, three high-density regions H, and three cam pins 43.
The cam pins 43 are disposed in the circumferential direction
between first center lines X1 which are positioned in the center in
the circumferential direction between adjacent high-density regions
H, and the high-density regions H.
Inventors: |
Iyoda; Makoto; (Osaka,
JP) ; Nakao; Suguru; (Hyogo, JP) ; Irie;
Shouichi; (Osaka, JP) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, NW
WASHINGTON
DC
20005-3096
US
|
Family ID: |
40337845 |
Appl. No.: |
12/059786 |
Filed: |
March 31, 2008 |
Current U.S.
Class: |
359/700 ;
425/573; 428/66.1 |
Current CPC
Class: |
Y10T 428/211 20150115;
G02B 7/102 20130101; B29C 45/0025 20130101; B29C 45/261 20130101;
B29C 2045/0027 20130101; B29L 2031/764 20130101 |
Class at
Publication: |
359/700 ;
425/573; 428/66.1 |
International
Class: |
G02B 15/14 20060101
G02B015/14; B29C 45/27 20060101 B29C045/27; B32B 3/02 20060101
B32B003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 3, 2007 |
JP |
2007-203524 |
Claims
1. A cylindrical molded article formed by injection molding,
comprising: a cylindrical portion; at least three cam grooves
formed on either the inner peripheral face or the outer peripheral
face of the cylindrical portion; at least three cam pins formed on
the other face of either the inner peripheral face or the outer
peripheral face of the cylindrical portion; and at least three
high-density regions on the face where the cam grooves are formed,
in which there is the highest proportion of the axial direction
dimension accounted for by the three or more cam grooves with
respect to the axial direction dimension of the cylindrical
portion, the cam pins are disposed between first center lines which
are positioned in the center in the circumferential direction
between the adjacent high-density regions, and first high-density
regions, each being one of the adjacent high-density regions, in
the circumferential direction.
2. The cylindrical molded article according to claim 1, further
comprising at least three low-density regions on the face where the
cam grooves are formed, in which there is the lowest proportion of
the axial direction dimension accounted for by the three or more
cam grooves with respect to the axial direction dimension of the
cylindrical portion, wherein the cam pins are disposed between the
high-density regions and the low-density regions in the
circumferential direction.
3. The cylindrical molded article according to claim 1, wherein the
cam pins are disposed between second center lines which are
positioned in the center in the circumferential direction between
the first high-density regions and the first center lines, and the
first high-density regions, in the circumferential direction.
4. The cylindrical molded article according to claim 1, wherein the
three or more cam pins are disposed at a constant pitch in the
circumferential direction.
5. The cylindrical molded article according to claim 2, wherein the
cam pins are disposed between second center lines which are
positioned in the center in the circumferential direction between
the first high-density regions and the first center lines, and the
first high-density regions, in the circumferential direction.
6. The cylindrical molded article according to claim 5, wherein the
three or more cam pins are disposed at a constant pitch in the
circumferential direction.
7. The cylindrical molded article according to claim 2, wherein the
three or more cam pins are disposed at a constant pitch in the
circumferential direction.
8. A lens barrel for supporting an imaging optical system,
comprising: the cylindrical molded article according to claim 1;
and a lens frame to which are fixed the lens group included in the
imaging optical system, and having at least three second cam pins
engaging with the cam grooves.
9. A camera, comprising: the lens barrel according to claim 8; an
imaging optical system supported by the lens barrel; an imaging
unit for capturing an optical image of a subject formed by the
imaging optical system; and an outer case supporting the lens
barrel.
10. An injection mold for injection molding a molding material to
obtain a cylindrical molded article having at least three cam
grooves and at least three cam pins, comprising: a first portion
having a cavity arranged to mold the cylindrical molded article; a
second portion having a sprue as a channel through which the
molding material is injected; a third portion having three first
runners connected to the sprue; and a fourth portion having gates
connecting the cavity and the three first runners. wherein the
first portion has a portion corresponding to the cam pins, and
three high-density regions in which there is the highest proportion
of the axial direction dimension accounted for by the portion
corresponding to the three or more cam grooves with respect to the
axial direction dimension of the cavity, and the cam pins are
disposed in the circumferential direction between first center
lines which are positioned in the center in the circumferential
direction between the adjacent high-density regions, and first
high-density regions, each being one of the adjacent high-density
regions.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Japanese Patent
Application No. JP2007-203524 filed on Aug. 3, 2007. The entire
disclosures of Japanese Patent Application No. JP2007-203524 is
hereby incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a cylindrical molded
article and an injection mold, and more particularly relates to a
cylindrical molded article used in the lens barrel of a camera and
an injection mold.
[0004] 2. Description of the Related Art
[0005] One conventional type of lens barrel is a multistage
retractable lens barrel. This kind of lens barrel is made up of a
plurality of cylindrical members of different diameter. To covert
the rotational motion of the cylindrical members into axial linear
motion, three cam grooves and three cam pins that engage with these
cam grooves are provided to a plurality of cylindrical members, for
example. The cam grooves are usually formed on the inner peripheral
part of the cylindrical members.
[0006] It is generally difficult to machine cam grooves on the
inner peripheral part of cylindrical members. Therefore, the
cylindrical members that make up a lens barrel are formed by
injection molding. An injection molding apparatus mainly includes
an injection mold, and an injection apparatus for injecting the
molten molding material into the mold. The injection apparatus can
be adjusted for molding material injection pressure and injection
speed.
[0007] The injection mold is provided with a cavity, a sprue, a
plurality of runners, and a plurality of gates. The cavity is a
hollow space used for form a molded article. The sprue is a channel
through which flows the molding material injected from the
injection apparatus. The runners guide the molding material from
the sprue to the cavity. The gates are constrictions for preventing
the back-flow of the molding material from the cavity to the
runners, and are disposed between the runners and the cavity. In
the case of a cylindrical molded article, a plurality of runners
are disposed at a constant pitch in the circumferential direction
so that the molding material will flow evenly. A plurality of gates
are also disposed at a constant pitch in the circumferential
direction.
[0008] Injection molding mainly includes a temperature adjustment
step in which the temperature of the metal mold is adjusted, a
filling step in which the mold is filled with the molding material,
and a pressure-holding cooling step in which the molded article is
cooled inside the mold. In the pressure-holding cooling step, the
pressure is held at a specific level by the injection apparatus.
This causes molding material to be supplied to portions where heat
shrinkage has occurred, and minimizes deformation of the molded
article due to heat shrinkage.
[0009] However, the wall thickness of the cylindrical molded
article is uneven because of the cam grooves. Consequently, the
thicker and thinner parts cool at different rates in the
pressure-holding cooling step, so the heat shrinkage varies from
place to place. As a result, there is a decrease in the circularity
of the cylindrical molded article, and the cylindrical molded
article cannot be obtained as designed. Even though the pressure is
maintained in the pressure-holding cooling step, it may be
impossible to suppress deformation of the molded article, depending
on the shape of the cam grooves.
[0010] If the cylindrical molded articles that make up a lens
barrel have decreased circularity, the cam grooves will be offset
in the radial direction from the designed positioned. As a result,
the lens group supported by the plurality of cylindrical molded
articles becomes out of position, and this adversely affects the
optical performance of the imaging optical system. Also, if the cam
grooves become misaligned in the radial direction with respect to
the designed position, there will be greater sliding resistance
between the cam grooves and the cam pins, which hinders smooth zoom
operation. As a result, greater drive force is necessary, and this
increases power consumption.
[0011] In view of this, as disclosed in Japanese Patents 3,523,249
and 2,995,509, correction of the injection mold is generally
carried out in conventional injection molding. More specifically,
with a conventional metal mold design, deformation due to heat
shrinkage is predicted on the basis of experimentation or
simulation. The mold is produced in the shape of the molded article
according to the predicted amount of deformation. Next, a prototype
is formed using the mold thus produced. The dimensions of the
various parts of the prototype are measured, and the differences
between the design and measured values are calculated. Metal mold
correction is performed using this dimensional error as an offset
value. In the case of cylindrical molded articles used in a lens
barrel, the cavity of the mold is formed as a cylindrical hollow
space that is not a true circle.
[0012] If there is a large difference between the design and
measured values, then more of the mold has to be machined, so mold
correction takes more time. Also, if there is a large difference
between the design and measured values, then there is greater
dimensional change in the various parts of a prototype formed with
the corrected mold than with a prototype formed with the initial
mold. Consequently, it is unlikely that a molded article will be
obtained with the design values after just one mold correction.
[0013] Conversely, if there is a small difference between the
design and measured values in a prototype produced by the initial
mold, mold machining takes less time and it is more likely that a
cylindrical molded article will be obtained with the design values
after a single mold correction.
[0014] As discussed above, it is preferable with an injection mold
for the error from the design values of a molded article to be kept
as small as possible.
[0015] On the other hand, there is a need in the field of digital
cameras for the main body to be as compact as possible to make the
product more portable. More specifically, there is a need to reduce
the size of the lens barrel, which is considered to be a major
factor in obtaining a smaller overall size. One way to make a lens
barrel smaller is to increase the change ratio of the focal
distance in zooming. As this is done, the shape of the cam grooves
becomes more complicated, and the difference in the wall thickness
of the cylindrical molded articles increases. Consequently,
reducing the size of a lens barrel leads to a decrease in
dimensional precision in cylindrical molded articles.
[0016] In addition, when cam pins are provided in the cylindrical
molded article, the position of the cam pins in the radial
direction changes with the deformation of the cylindrical molded
article in the radial direction. For this reason, it is thought a
case that the cam pins will not be able to fit in the corresponding
cam grooves, or a case that the cam pins will unnecessarily
interfere with the cam grooves, and so forth.
[0017] However, with the prior art discussed above, all that was
proposed was a method for measuring dimensional error, or a method
for predicting dimensional error by simulation and factoring this
error into the metal mold design.
[0018] When a cylindrical molded article having a cam groove is
injection molded, there seems to be some kind of relationship
between the circularity and shape of the cam groove, but the
details of this relationship are not yet clear. Therefore, with a
conventional injection mold, even if changes are made to the shape
of the cam grooves, there is the risk that more mold corrections
will be necessary.
SUMMARY OF THE INVENTION
[0019] It is an object of the present invention to provide a
cylindrical molded article and an injection mold, with which
manufacturing cost can be reduced and dimensional precision can be
increased.
[0020] The cylindrical molded article according to a first aspect
of the present invention is a member molded by injection molding.
This cylindrical molded article includes a cylindrical portion, at
least three cam grooves, at least three cam pins, and at least
three high-density regions. The cam grooves are formed on either
the inner peripheral face or the outer peripheral face of the
cylindrical portion. The cam pins are formed on the other face of
either the inner peripheral face or the outer peripheral face of
the cylindrical portion. The high-density regions on the face where
the cam grooves are formed are where there is the highest
proportion of the axial direction dimension accounted for by the
three or more cam grooves with respect to the axial direction
dimension of the cylindrical portion. The cam pins are disposed
between first center lines which are positioned in the center in
the circumferential direction between the adjacent high-density
regions, and first high-density regions, each being one of the
adjacent high-density regions, in the circumferential
direction.
[0021] With this cylindrical molded article, since the cam pins are
disposed between the first high-density regions and the first
center lines in the circumferential direction, the cam pins can be
disposed in areas around the center between portions pushed inward
to the inner side in the radial direction and portions pushed
outward to the outer side in the radial direction in the
cylindrical portion. As a result, the positional precision in the
radial direction of the cam pins will not be easily affected by the
deformation of the cylindrical portion, and the number of mold
corrections can be reduced. In other words, with this cylindrical
molded article, the dimensional precision can be ensured while the
manufacturing cost is reduced.
[0022] The cylindrical molded article according to a second aspect
of the present invention is the cylindrical molded article of the
first aspect, wherein the cylindrical molded article further
includes at least three low-density regions. The low-density
regions on the face where the cam grooves are formed are where
there is the lowest proportion of the axial direction dimension
accounted for by the three or more cam grooves with respect to the
axial direction dimension of the cylindrical portion. The cam pins
are disposed between the high-density regions and the low-density
regions in the circumferential direction.
[0023] The cylindrical molded article according to a third aspect
of the present invention is the cylindrical molded article of the
first or the second aspect, wherein the cam pins are disposed
between second center lines that are positioned in the center in
the circumferential direction between the first high-density
regions and the first center lines, and the first high-density
regions, in the circumferential direction.
[0024] The cylindrical molded article according to a fourth aspect
of the present invention is the cylindrical molded article of any
one of the first through third aspects, wherein the three or more
cam pins are disposed at a constant pitch in the circumferential
direction.
[0025] The lens barrel according to a fifth aspect of the present
invention is a lens barrel for supporting an imaging optical
system. This lens barrel includes the cylindrical molded article of
any one of the first to fourth aspects, and a lens frame. The lens
frame has the lens group included in the imaging optical system
fixed thereto, and has at least three second cam pins that engage
with the cam grooves.
[0026] The camera according to a sixth aspect of the present
invention includes the lens barrel of the fifth aspect, an imaging
optical system supported by the lens barrel, an imaging unit for
capturing an optical image of a subject formed by the imaging
optical system, and an outer case supporting the lens barrel.
[0027] The injection mold according to a seventh aspect of the
present invention is a mold for injection molding a molding
material to obtain a cylindrical molded article having at least
three cam grooves. This mold includes a first portion, a second
portion, a third portion, and a fourth portion. The first portion
has a cavity arranged to mold the cylindrical molded article. The
second portion has a sprue as a channel through which the molding
material is injected. The third portion has three first runners
connected to the sprue. The fourth portion has gates that connect
the cavity and the three first runners. The first portion has at
least three cam pins, and three high-density regions in which there
is the highest proportion of the axial direction dimension
accounted for by the portion corresponding to the three or more cam
grooves with respect to the axial direction dimension of the
cavity. The cam pins are disposed in the circumferential direction
between first center lines that are positioned in the center in the
circumferential direction between the adjacent high-density
regions, and first high-density regions, each being one of the
adjacent high-density regions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Referring now to the attached drawings which form a part of
this original disclosure:
[0029] FIG. 1 is a schematic perspective view of a digital
camera;
[0030] FIG. 2 is a schematic perspective view of a digital
camera;
[0031] FIG. 3 is an exploded perspective view of a lens barrel;
[0032] FIGS. 4A and 4B are schematic diagrams of a molded article
80 and an injection mold 70;
[0033] FIG. 5 is a development view of the inner peripheral side of
a drive frame;
[0034] FIG. 6 is a schematic diagram showing the relationship
between the disposition of cam grooves and the amount of deviation
in circularity of a drive frame, and
[0035] FIG. 7 is a schematic diagram of the method for determining
the high-density regions and low-density regions.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] Selected embodiments of the present invention will now be
explained with reference to the drawings. It will be apparent to
those skilled in the art from this disclosure that the following
descriptions of the embodiments of the present invention are
provided for illustration only and not for the purpose of limiting
the invention as defined by the appended claims and their
equivalents.
[0037] An embodiment according to the present invention will now be
described in detail with reference to the drawings.
[0038] 1. Overview of Digital Camera
[0039] A digital camera 1 in which a cylindrical molded article
according to the present invention is used will be described with
reference to FIGS. 1 and 2. FIGS. 1 and 2 show schematic
perspective views of the digital camera 1. FIG. 1 shows the
situation when a lens barrel 3 is in an image capture state. In
addition, this digital camera 1 is characterized by the disposition
of cam pins 43 of drive frame 34. The disposition of the cam pins
43 will be described later.
[0040] The digital camera 1 is a camera for acquiring an image of a
subject. A multistage retractable lens barrel 3 is installed in the
digital camera 1 in order to afford higher magnification and a more
compact size.
[0041] In the following description, the six sides of the digital
camera 1 are defined as follows.
[0042] The side that faces the subject when an image is captured
with the digital camera 1 is called the front face, and the
opposite side is called the rear face. When an image is captured
such that the top and bottom of the subject in the vertical
direction coincide with the short-side top and bottom of a
rectangular image (generally with an aspect ratio (the ratio of the
long side to the short side) of 3:2, 4:3, 16:9, etc.) captured by
the digital camera 1, the side of the camera facing upward
(vertically) is called the top face, and the opposite side is
called the bottom face. Further, when an image is captured such
that the top and bottom of the subject in the vertical direction
coincide with the short-side top and bottom of a rectangular image
captured by the digital camera 1, the side of the camera that is to
the left when viewed from the subject side is called the left face,
and the opposite side is called the right face. The above
definitions are not intended to limit the orientation in which the
digital camera 1 is used.
[0043] According to the above definitions, FIG. 1 is a perspective
view of the front, top, and left faces.
[0044] In addition to the six sides of the digital camera 1, the
six sides of the various constituent members disposed in the
digital camera 1 are similarly defined. That is, the above
definitions apply to the six sides of the various constituent
members when thev have been disposed in the digital camera 1.
[0045] Also, as shown in FIG. 1, there is defined a
three-dimensional coordinate system (right-hand system) having a Y
axis that is parallel to the optical axis A of an imaging optical
system O (discussed below). With this definition, the direction
from the rear face side toward the front face side along the
optical axis A is the Y axis positive direction, the direction from
the right face side toward the left face side perpendicular to the
optical axis A is the X axis positive direction, and the direction
from the bottom face side toward the top face side perpendicular to
the X and Y axes is the Z axis positive direction.
[0046] This XYZ coordinate system will be referred to in the
following description of the drawings. That is, the X axis positive
direction, the Y axis positive direction, and the Z axis positive
direction in the drawings indicate the same respective
directions.
[0047] 2. Overall Structure of a Digital Camera
[0048] As shown in FIGS. 1 and 2, the digital camera 1 mainly
includes an outer case 2 that holds the various units, an imaging
optical system O that forms an optical image of the subject, and a
lens barrel 3 that movably supports the imaging optical system
O.
[0049] The imaging optical system O is made up of a plurality of
lens groups, and these lens groups are disposed in a state of being
aligned in the Y axis direction. The lens barrel 3 has a multistage
retractable configuration, and is supported by the outer case 2.
The plurality of lens groups are supported by the lens barrel 3 to
be relatively movable in the Y axis direction. The configuration of
the lens barrel 3 will be described in detail below.
[0050] A CCD unit 21 serving as an imaging unit that subjects
optical images to photoelectric conversion, and an image storing
unit 16 that stores the images acquired by the CCD unit 21 are
built into the outer case 2. A liquid crystal monitor 15 for
displaying the images acquired by the CCD unit 21 is provided to
the rear face of the outer case 2.
[0051] A shutter release button 11, a control dial 12, a power
switch 13, and a zoom adjustment lever 14 are provided to the top
face of the outer case 2 so that the user can capture images and
perform other such operations. The shutter release button 11 is a
button for inputting the exposure timing. The control dial 12 is a
dial for making various settings related to image capture. The
power switch 13 is used to switch the digital camera 1 on and off.
The zoom adjustment lever 14 is used to adjust the zoom
magnification, and can rotate over a specific angle range around
the shutter release button 11.
[0052] FIGS. 1 and 2 show only the main configuration of the
digital camera 1, and therefore components other than those
discussed above may be provided to the digital camera 1.
[0053] 3. Configuration of Lens Barrel
[0054] The overall configuration of the lens barrel 3 will be
described with reference to FIG. 3. FIG. 3 is an exploded
perspective view of the lens barrel 3.
[0055] As shows in FIG. 3, the lens barrel 3 mainly includes a base
plate 31 fixed to the outer case 2, a zoom motor 32 fixed to the
base plate 31 and serving as a drive source, a stationary frame 33
that holds various frame members between itself and the base plate
31, a drive frame 34 to which the drive force of the zoom motor 32
is inputted, and a straight-movement frame 35 that is supported by
the stationary frame 33 to be relatively movable in the Y axis
direction. A CCD sensor 22 of the CCD unit 21 is attached to the
base plate 31. An example of the zoom motor 32 is a stepping
motor.
[0056] The lens barrel 3 further includes a first lens frame 36
that supports a first lens group G1, a second lens frame 37 that
supports a second lens group G2, and a third lens frame 38 that
supports a third lens group G3. The first lens group G1 is, for
example, a lens group having negative power overall, and takes in
light from the subject. The second lens group G2 is, for example, a
lens group having positive power overall. The third lens group G3
is, for example, a lens group having positive power for adjusting
the focal point. The imaging optical system O is made up of the
first lens group G1, the second lens group G2, and the third lens
group G3.
[0057] 3.1. Stationary Frame
[0058] The stationary frame 33 is a member for guiding the drive
frame 34, and makes up a member on the stationary side of the lens
barrel 3 along with the base plate 31. The stationary frame 33 is
fixed by screws to the base plate 31. The stationary frame 33
mainly includes a stationary frame main body 33a that makes up the
main part, and a drive gear 33b that is rotatably supported by the
stationary frame main body 33a.
[0059] The stationary frame main body 33a is fixed to the base
plate 31, and the drive frame 34 is disposed inside the inner
periphery thereof. The drive gear 33b is a member for transmitting
the drive force of the zoom motor 32 to the drive frame 34, and
meshes with a gear (not shown) of the zoom motor 32. Three cam
grooves 33c for guiding the drive frame 34, and three
straight-movement grooves 33d for guiding the straight-movement
frame 35 are formed on the inner peripheral part of the stationary
frame main body 33a. The cam grooves 33c are spaced equally in the
circumferential direction. The straight-movement grooves 33d extend
in the Y axis direction, and are spaced equally in the
circumferential direction.
[0060] 3.2. Drive Frame
[0061] The drive frame 34 is a member for guiding the first lens
frame 36 and the second lens frame 37, and is disposed inside the
inner periphery of the stationary frame 33. The drive frame 34
mainly includes a substantially cylindrical drive frame main body
34a that is disposed inside the inner periphery of the stationary
frame main body 33a.
[0062] Three cam pins 43 are provided as cam members on the outer
peripheral part of the drive frame main body 34a, and three first
cam grooves 34c and three second cam grooves 34d are formed on the
inner peripheral part. The first cam grooves 34c are grooves for
guiding the first lens frame 36. The second cam grooves 34d are
grooves for guiding the second lens frame 37. The three first cam
grooves 34c are spaced equally in the circumferential direction.
The three second cam grooves 34d are spaced equally in the
circumferential direction. The three cam pins 43 are spaced equally
in the circumferential direction, and engage with the three cam
grooves 33c of the stationary frame 33. That is, the drive frame 34
is supported by the stationary frame 33 via the cam pins 43.
[0063] A gear portion 34e is formed on the outer peripheral part of
the drive frame main body 34a. The gear portion 34e meshes with the
drive gear 33b of the stationary frame 33. As a result, the drive
force of the zoom motor 32 is transmitted through the drive gear
33b to the drive frame 34.
[0064] The drive frame 34 is driven around the optical axis A (the
R1 direction and the R2 direction) by the drive force of the zoom
motor 32. When the camera 1 changes from their retracted state to
their image capture state, the drive frame 34 is driven to the R1
side by the zoom motor 32. As a result, the cam pins 43 move along
the cam grooves 33c of the stationary frame 33, and the drive frame
34 moves to the Y axis direction positive side relative to the
stationary frame 33. When the camera 1 changes from their image
capture state to their retracted state, the drive frame 34 is
driven to the R2 side by the zoom motor 32. As a result, the drive
frame 34 moves to the Y axis direction negative side relative to
the stationary frame 33.
[0065] Thus, the drive frame 34 is movable in the Y axis direction
while rotating relative to the stationary frame 33, according to
the shape of the cam grooves 33c.
[0066] 3.3. Straight-Movement Frame
[0067] The straight-movement frame 35 is a member for preventing
the rotation of the first lens frame 36 relative to the stationary
frame 33, and is disposed inside the inner periphery of the drive
frame 34. The straight-movement frame 35 mainly includes a
cylindrical straight-movement frame main body 35a and three
straight-movement pins 35b formed on the outer peripheral part of
the straight-movement frame main body 35a.
[0068] The straight-movement pins 35b are disposed on the Y axis
direction negative side of the straight-movement frame main body
35a so as not to interfere with the drive frame 34, and engage with
the straight-movement grooves 33d in the stationary frame 33. That
is, the straight-movement frame 35 is supported by the stationary
frame 33 to be relatively straight movable in the Y axis
direction.
[0069] A bayonet groove 35e is formed on the outer peripheral part
of the straight-movement frame main body 35a. A bayonet tab 34f
(not shown) formed on the inner peripheral part of the drive frame
34 engages with the bayonet groove 35e. This allows the
straight-movement frame 35 to rotate relative to the drive frame 34
and to move integrally in the Y axis direction.
[0070] Specifically, when the drive frame 34 rotates relative to
the stationary frame 33, the straight-movement frame 35 moves along
with the drive frame 34 in the Y axis direction without rotating
relative to the stationary frame 33 (while rotating relative to the
drive frame 34).
[0071] Three first guide grooves 35c and three second guide grooves
35d that extend in the Y axis direction are formed in the
straight-movement frame main body 35a. The three first guide
grooves 35c are spaced equally in the circumferential direction,
and the three second guide grooves 35d are spaced equally in the
circumferential direction. Cam pins 36b (discussed below) of the
first lens frame 36 are inserted in the first guide grooves 35c.
Cam pins 37b (discussed below) of the second lens frame 37 are
inserted in the second guide grooves 35d. That is, the rotation of
the first lens frame 36 and the second lens frame 37 relative to
the stationary frame 33 is restricted by the straight-movement
frame 35. Furthermore, movement of the first lens frame 36 and the
second lens frame 37 in the Y axis direction is not restricted by
the first guide grooves 35c and the second guide grooves 35d.
[0072] 3.4. First Lens Frame
[0073] The first lens frame 36 is a member supporting the first
lens group G1 to be relatively movable in the Y axis direction, and
is disposed inside the inner periphery of the straight-movement
frame 35. The first lens frame 36 mainly includes a first lens
frame main body 36a in the interior of which is held the first lens
group G1, and the three cam pins 36b provided on the outer
peripheral part of the first lens frame main body 36a. The cam pins
36b are passed through the first guide grooves 35c and engage with
the first cam grooves 34c of the drive frame 34.
[0074] When the drive frame 34 rotates relative to the stationary
frame 33, the cam pins 36b move along the first cam grooves 34c.
The movement of the cam pins 36b in the rotary direction here is
restricted by the first guide grooves 35c of the straight-movement
frame 35. Therefore, the cam pins 36b move only in the Y axis
direction along the first cam grooves 34c and the first guide
grooves 35c. Thus, the first lens frame 36 is movable in the Y axis
direction relative to the drive frame 34 according to the shape of
the first cam grooves 34c, without rotating relative to the
stationary frame 33.
[0075] 3.5. Second Lens Frame
[0076] The second lens frame 37 is a member supporting the second
lens group G2 to be relatively movable in the Y axis direction, and
is disposed inside the inner periphery of the straight-movement
frame 35 and on the Y axis direction negative side of the first
lens frame 36. The second lens frame 37 mainly includes a first
frame 50 and second frame 59 in the interior of which is held the
second lens group G2, and the three cam pins 37b provided on the
outer peripheral part of the first frame 50. The cam pins 37b are
passed through the second guide grooves 35d and engage with the
second cam grooves 34d of the drive frame 34.
[0077] When the drive frame 34 rotates relative to the stationary
frame 33, the cam pins 37b move along the second guide grooves 35d.
The movement of the cam pins 37b here in the rotational direction
is restricted by the second guide grooves 35d of the
straight-movement frame 35. Therefore, just as with the first lens
frame 36, the cam pins 37b move only in the Y axis direction along
the second cam grooves 34d and the second guide grooves 35d.
[0078] Thus, the second lens frame 37 is movable in the Y axis
direction relative to the drive frame 34 according to the shape of
the second cam grooves 34d without rotating relative to the
stationary frame 33.
[0079] 3.6. Third Lens Frame
[0080] The third lens frame 38 is a member supporting the third
lens group G3 to be relatively movable in the Y axis direction, and
is supported by focus shafts 31a and 31b of the base plate 31 to be
relatively movable in the Y axis direction. The third lens frame 38
is driven by a focus motor 39 fixed to the base plate 31. The focus
motor 39 moves the third lens frame 38 in the Y axis direction
relative to the base plate 31.
[0081] 3.7. Summary
[0082] To summarize the above configuration, the first lens frame
36 and the second lens frame 37 can be moved in the direction along
the optical axis A by the zoom motor 32 via the stationary frame
33, the drive frame 34, and the straight-movement frame 35. The
third lens frame 38 can be moved in the direction along the optical
axis A by the focus motor 39.
[0083] Therefore, this configuration results in a retractable lens
barrel 3 that allows adjustment of the focus and the zoom
magnification of the imaging optical system O.
[0084] 4. Cylindrical Molded Article and Injection Mold
[0085] A cylindrical molded article and an injection mold according
to this embodiment will be described. Here, drive frame 34 will be
described as an example of a molded article. In FIGS. 4A and 4B,
schematic diagrams of a molded article 80 and an injection mold 70
are shown. FIG. 4A is a schematic perspective view of the molded
article 80 and the injection mold 70, and FIG. 4B is a plan view of
the molded article 80 seen in the axial direction.
[0086] 4.1. Molded Article
[0087] As shown in FIGS. 4A and 4B, the molded article 80 is made
from a synthetic resin removed from the mold 70 after injection
molding. Example of the synthetic resin is a polycarbonate or other
such a thermoplastic resin. The molded article 80 mainly includes
the drive frame 34 as a cylindrical molded article, and a channel
portion 81. The channel portion 81 is separated from the drive
frame 34 after injection molding. As discussed above, a total of
six cam grooves (the first cam grooves 34c and the second cam
grooves 34d) are formed on the inner peripheral side of the drive
frame 34.
[0088] The channel portion 81 is a portion formed by a channel in
the mold 70 during injection molding, and includes a sprue portion
82, six runner portions 84a linked to the sprue portion 82, and six
gate portions 84b. The runner portions 84a are disposed at a
constant pitch in the circumferential direction. The gate portions
84b are disposed at a constant pitch in the circumferential
direction, for example, and are disposed on an annular end face of
the drive frame 34 that is directed to the axial direction.
[0089] 4.2. Disposition of the Cam Pins
[0090] This drive frame 34 is characterized by the disposition of
the cam pins 43. The disposition of the cam pins 43 will be
described with reference to FIGS. 5 and 6. FIG. 5 shows a
development view of the inner peripheral side of the drive frame
34. FIG. 6 shows the relationship between the disposition of the
cam grooves 34d on the inner peripheral side of the drive frame 34
and the amount of deviation in circularity. Here, the disposition
will be described using the constitution of the molded article 80,
but since the constitution of the molded article 80 corresponds to
the constitution of the mold 70, the following description can be
considered to apply to the mold 70 as well, and not just to the
molded article 80.
[0091] As shown in FIG. 4B, the three cam pins 43 are disposed at a
constant pitch in the circumferential direction. As shown in FIG.
5, the three first cam grooves 34c and the three second cam grooves
34d are formed on the inner peripheral side of the drive frame 34.
The three first cam grooves 34c all have the same shape, and are
disposed at a constant pitch in the circumferential direction. The
three second cam grooves 34d all have the same shape, and are
disposed at a constant pitch in the circumferential direction. The
first cam grooves 34c and the second cam grooves 34d are
alternately disposed in the circumferential direction so as not to
cross each other.
[0092] The first cam grooves 34c each include a first cam groove
main body C2 and a first conducting groove C3 formed at one end of
the first cam groove main body C2. The first conducting groove C3
extends in the axial direction, and passes through the end of the
drive frame main body 34a. The other end C1 of the first cam groove
main body C2 does not pass through in the axial direction.
[0093] The second cam grooves 34d each include a second cam groove
main body D2, a second conducting groove D1 formed at one end of
the second cam groove main body D2, and a third conducting groove
D3 formed at the other end of the second cam groove main body D2.
The second conducting groove D1 and the third conducting groove D3
extend in the axial direction, and pass through the end of the
drive frame main body 34a.
[0094] In this embodiment, the first cam grooves 34c have the same
width from the end C1 to the first conducting groove C3. The second
cam grooves 34d have the same width from the second conducting
groove D1 to the third conducting groove D3. Also, the first cam
grooves 34c and the second cam grooves 34d have the same width.
[0095] The drive frame 34 does not have a constant wall thickness
because of the first cam grooves 34c and the second cam grooves
34d. More specifically, on the inner peripheral face of the drive
frame 34, there are three high-density regions H in which the
proportion accounted for by the cam grooves is highest, and three
low-density regions L in which the proportion accounted for by the
cam grooves is lowest. The three high-density regions H are
disposed at a constant pitch in the circumferential direction. The
three low-density regions L are disposed at a constant pitch in the
circumferential direction.
[0096] The high-density regions H are regions in which there is the
highest proportion of the axial direction dimension accounted for
by the first cam grooves 34c and the second cam grooves 34d with
respect to the axial direction dimension of the drive frame 34, on
the inner peripheral face of the drive frame 34. The low-density
regions L are regions in which there is the lowest proportion of
the axial direction dimension accounted for by the first cam
grooves 34c and the second cam grooves 34d with respect to the
axial direction dimension of the drive frame 34, on the inner
peripheral face of the drive frame 34. As shown in FIG. 5, the
high-density regions H coincide with the portion in which the third
conducting groove D3 extends in the axial direction. The
low-density regions L coincide with the portion in which the first
cam grooves 34c and the second cam grooves 34d extend in the
circumferential direction.
[0097] The method for determining the high-density regions H and
the low-density regions L will be described. As shown in FIG. 7, a
case in which two grooves are formed, a first cam groove 34c and a
second cam groove 34d is assumed. W0 is defined as the axial
direction dimension of the drive frame 34 (more specifically, the
drive frame main body 34a), W1 is defined as the axial direction
dimension of the first cam groove 34c, and W2 is defined as the
axial direction dimension of the second cam groove 34d. In this
case, P, which is "the proportion of the axial direction dimension
accounted for by the first cam grooves 34c and the second cam
grooves 34d with respect to the axial direction dimension of the
drive frame 34", is expressed by P=(W1+W2)/W0. The clusters of
lines where the proportion P is highest are the high-density
regions H, and the clusters of lines where the proportion P is
lowest are the low-density regions L.
[0098] The disposition of cam pins 43 and the cam grooves will now
be described in detail.
[0099] As shown in FIG. 6, as a result of examining the
relationship between the shape of the cam grooves 34d and the
curvature deformation during molding of the drive frame 34
(cylindrical molded article), the drive frame 34 tends to deform to
the inner side in the radial direction in the high-density regions
H, and deform to the outer side in the radial direction in the
low-density regions L. This is possibly because the thickness of
the drive frame 34 is thin and bends easily in the high-density
regions H compared to the surrounding portions. In other words, it
is understood that the deformation pattern of the drive frame 34 is
mainly determined by the position of the high-density regions H.
This results in the cam pins 43 to be out of position in the radial
direction to the inner side if the cam pins 43 are disposed in
areas around the high-density regions H, and results in the cam
pins 43 to be out of position in the radial direction to the outer
side if the cam pins 43 are disposed in areas around the
low-density regions L arranged near the center in the
circumferential direction between the high-density regions H. As a
result, the positional precision of the cam pins 43 in the radial
direction does not satisfy the designed tolerance.
[0100] Consequently, the position of the cam pins 43 are determined
mainly based on the high-density regions H in this drive frame 34,
so that the positional precision of the cam pins 43 satisfies the
designed tolerance. More specifically, as shown in FIGS. 5 and 6,
the cam pins 43 are disposed between the high-density regions H and
the low density regions L in the circumferential direction. The cam
pins 43 are disposed in the circumferential direction between the
high-density regions H (first high-density regions) and first
center lines X1, which are positioned in the center in the
circumferential direction between the adjacent high-density regions
H. The high-density regions H are regions having almost the same
circumferential direction dimension as the width of the third
conducting grooves D3, and have base lines H1, which are center
lines in the circumferential direction. Since the first center
lines X1 are disposed in the center in the circumferential
direction between the adjacent base lines H1, the distance (L1)
between the base lines H1 and the first center lines X1 in the
circumferential direction is equal.
[0101] Furthermore, the cam pins 43 are disposed in the
circumferential direction between the high-density regions H and
second center lines X2, which are positioned in the center in the
circumferential direction between the high-density regions H and
the first center lines X1. More specifically, the second center
lines X2 are disposed in the center in the circumferential
direction between the base lines H1 of the high-density regions H
and the first center lines X1. The distance between the base lines
H1 and the second center lines X2 in the circumferential direction
is the same length (L2) as the distance between the second center
lines X2 and the first center lines X1 in the circumferential
direction. The cam pins 43 are disposed in areas around the second
center lines X2, between the second center lines X2 and the base
lines H1 which are nearest to the second center lines X2 in the
circumferential direction. In other words, in the case that the
regions between the adjacent high-density regions H are divided
into four equal parts in the circumferential direction, the
position of the cam pins 43 are set in the one-fourth region from
the high-density regions H.
[0102] In this way, by determining the position of the cam pins 43
based on the high-density regions H and dispose the cam pins 43 in
areas around the second center lines X2, the cam pins 43 can be
disposed in areas around the center in the circumferential
direction between the portion pushed inward to the inner side in
the radial direction (for example, the high-density regions H) and
the portion pushed outward to the outer side in the radial
direction (for example, the low-density regions L). Consequently,
the positional precision of the cam pins 43 in the radial direction
will not be affected by the deformation of the drive frame main
body 34a easily, and the number of mold corrections can be reduced.
As a result, with this drive frame 34, dimensional precision can be
ensured while the manufacturing cost is reduced.
[0103] 4.3. Injection Mold
[0104] The injection mold 70 is a mold used for injection molding,
and mainly includes a first portion 71, a second portion 72, a
third portion 73, and a fourth portion 79. The mold 70 is made up
of a plurality of parts, but the first portion 71 to the fourth
portion 79 are divided in the sense of being portions having
different functions. Therefore, the portions 71 to 73 and 79 are
not limited to being made up of different parts.
[0105] A cavity 71a for molding the drive frame 34 is formed in the
first portion 71. The cavity 71a is defined by combining two mold
parts (not shown), for example. Since the drive frame 34 having the
first cam grooves 34c, the second cam grooves 34d, and the cam pins
43, is molded in the cavity 71a, the first portion 71 includes
portions corresponding to the first cam grooves 34c, portions
corresponding to the second cam grooves 34d, and portions
corresponding to the cam pins 43.
[0106] A sprue 72a through which the molten molding material is
injected from the injection apparatus (not shown) is formed in the
second portion 72. For instance, the sprue 72a is formed by a
cylindrical sprue bush (not shown). The sprue portion 82 is molded
by the sprue 72a.
[0107] Six runners 74a connected to the sprue 72a are formed in the
third portion 73. Six gates 74b are formed in the fourth portion
79. One end of the runners 74a is connected to the sprue 72a, and
the other end is connected to the gates 74b. The runner portions
84a are molded by the runners 74a, and the gate portions 84b are
molded by the gates 74b.
[0108] 5. Operation of Digital Camera
[0109] The operation of the digital camera 1 will be described with
reference to FIGS. 1 to 3.
[0110] 5.1. When Power is Off
[0111] When the power switch 13 is in its off position, the lens
barrel 3 is stopped in its retracted position (the state in which
the lens barrel 3 is at its shortest in the Y axis direction), so
that the lens barrel 3 will fit within the external dimensions of
the outer case 2 in the Y axis direction.
[0112] 5.2. When Power is On
[0113] When the power switch 13 is switched on, power is supplied
to the various units, and the lens barrel 3 is driven from its
retracted state to its image capture state. More specifically, the
drive frame 34 is driven by the zoom motor 32 by a specific angle
to the R1 side relative to the stationary frame 33. As a result,
the drive frame 34 moves to the Y axis direction positive side
relative to the stationary frame 33 while rotating relative to the
stationary frame 33 according to the shape of the cam grooves
33c.
[0114] When the drive frame 34 rotates and moves straight relative
to the stationary frame 33, the first lens frame 36 and the second
lens frame 37 move along with the drive frame 34 to the Y axis
direction positive side relative to the stationary frame 33. The
first lens frame 36 and the second lens frame 37 do not rotate
relative to the stationary frame 33 at this point.
[0115] The first lens frame 36 and the second lens frame 37 move
along with the drive frame 34 to the Y axis direction positive side
while moving in the Y axis direction relative to the drive frame 34
according to the shape of the first cam grooves 34c and the second
cam grooves 34d. At this time the first lens frame 36 and the
second lens frame 37 move relatively in the Y axis direction.
Specifically, the first lens frame 36 and the second lens frame 37
move in the Y axis direction relative to the stationary frame 33 by
an amount that is larger (or smaller) than the amount of movement
of the drive frame 34 in the Y axis direction.
[0116] When the rotation of the drive frame 34 is stopped, movement
of the first lens frame 36 and the second lens frame 37 in the Y
axis direction also stops, and the lens barrel 3 is in its image
capture state.
[0117] 5.3. Zoom Operation During Image Capture
[0118] When the zoom adjustment lever 14 is operated to the
telephoto side, the drive frame 34 is driven by the zoom motor 32
to the R1 side relative to the stationary frame 33, according to
the rotational angle and operation duration of the zoom adjustment
lever 14. As a result, the drive frame 34, the first lens frame 36,
and the second lens frame 37 move together to the Y axis direction
positive side relative to the stationary frame 33, and the zoom
magnification of the imaging optical system O is increased.
[0119] When the zoom adjustment lever 14 is operated to the
wide-angle side, the drive frame 34 is driven by the zoom motor 32
to the R2 side relative to the stationary frame 33, according to
the rotational angle and operation duration of the zoom adjustment
lever 14. As a result, the drive frame 34, the first lens frame 36,
and the second lens frame 37 move together to the Y axis direction
negative side relative to the stationary frame 33, and the zoom
magnification of the imaging optical system O is decreased.
[0120] 6. Characteristics
[0121] The following are characteristics of the molded article 80,
the lens barrel 3, the digital camera 1, and the injection mold
70.
[0122] 6.1.
[0123] With this molded article 80, the cam pins 43 are disposed
between the high-density regions H and the first center lines X1 in
the circumferential direction, and more specifically, disposed in
areas around the second center lines X2 located in the center in
the circumferential direction between the high-density regions H
and the first center lines X1. Consequently, by disposing the cam
pins 43 in areas around the second center lines X2, the cam pins 43
can be disposed in areas around the center in the circumferential
direction between the portions pushed inward to the inner side in
the radial direction (for example, high-density regions H) and the
portions pushed outward to the outer side in the radial direction
(for example, low-density regions L). As a result, the positional
precision of the cam pins 43 in the radial direction will not be
easily affected by the deformation of the drive frame main body
34a, and the number of mold corrections can be reduced. As a
result, with this drive frame 34, the dimensional precision can be
ensured while the manufacturing cost is reduced.
[0124] 6.2.
[0125] As discussed above, since the drive frame 34 or other such
molded article 80 with dimensional precision ensured is used for
this lens barrel 3, the positional precision of the lens group is
stabilized and the optical performance of the imaging optical
system O is stabilized. Also, with this molded article 80, the
number of mold corrections is reduced, and the manufacturing cost
can be reduced. In this way, the optical performance of the lens
barrel 3 can be stabilized while the manufacturing cost thereof is
reduced. Furthermore, with this digital camera 1, since the optical
performance of the imaging optical system O is stabilized, the
quality of the acquired image is stabilized.
7. OTHER EMBODIMENTS
[0126] The cylindrical molded article, lens barrel, camera, and
injection mold according to the present invention are not limited
to the above embodiment, and various modifications and alterations
can be made herein without departing from the scope of the present
invention.
[0127] 7.1.
[0128] The number of gate portions 84b is not limited to six
locations. The number of gate portions 84b may be more or fewer
than six.
[0129] 7.2.
[0130] In the above embodiment, the case in which the cam grooves
34d are formed on the inner peripheral face of the drive frame 34
is described. However, it is also possible for the cam grooves 34d
to form on the outer peripheral face of the drive frame 34 and the
cam pins 43 to form on the inner peripheral face. In addition, it
is also possible for the cam grooves to form on the inner
peripheral face and the outer peripheral face of the drive frame
34. In this case, the high-density regions H and the low-density
regions L may be determined based on the cam grooves on the inner
peripheral face, or based on the cam grooves on the outer
peripheral face.
[0131] 7.3.
[0132] In the above embodiment, the disposition of the cam pins 43
is determined based on the base lines H1, the first center lines
X1, and the second center lines X2. However, the position of the
cam pins 43 may be determined from the positional relationship
between the high-density regions H and the low-density regions
L.
General Interpretation of Terms
[0133] In understanding the scope of the present invention, the
term "configured" as used herein to describe a component, section
or part of a device includes hardware and/or software that is
constructed and/or programmed to carry out the desired
function.
[0134] In understanding the scope of the present invention, the
term "comprising" and its derivatives, as used herein, are intended
to be open ended terms that specify the presence of the stated
features, elements, components, groups, integers, and/or steps, but
do not exclude the presence of other unstated features, elements,
components, groups, integers and/or steps. The foregoing also
applies to words having similar meanings such as the terms,
"including", "having" and their derivatives. Also, the terms
"part," "section," "portion," "member" or "element" when used in
the singular can have the dual meaning of a single part or a
plurality of parts.
[0135] Terms that are expressed as "means-plus function" in the
claims should include any structure that can be utilized to carry
out the function of that part of the present invention. Finally,
terms of degree such as "substantially", "about" and
"approximately" as used herein mean a reasonable amount of
deviation of the modified term such that the end result is not
significantly changed. For example, these terms can be construed as
including a deviation of at least .+-.5% of the modified term if
this deviation would not negate the meaning of the word it
modifies.
[0136] While only selected embodiments have been chosen to
illustrate the present invention, it will be apparent to those
skilled in the art from this disclosure that various changes and
modifications can be made herein without departing from the scope
of the invention as defined in the appended claims. Furthermore,
the foregoing descriptions of the embodiments according to the
present invention are provided for illustration only, and not for
the purpose of limiting the invention as defined by the appended
claims and their equivalents. Thus, the scope of the invention is
not limited to the disclosed embodiments.
* * * * *